Our "Sunday spotlight" shines this weekend on Boston strong. A remarkable mother and daughter who have written a marathon story for the record books. It's brought to us by new England patriot quarterback Tom Brady. The second bomb had just exploded. Confusion. Terror. Kris and Kayla biagiotti scrambled across the finish line. Two of the very last runners to make it that day. But it also was a first. The first mother/daughter team ever to run the Boston marathon. I remember looking down and she still had her arms up and she's still smiling. I'm saying, she's okay. In her mind, she's thinking that this commotion that's going on is fireworks or, you know, some sort of celebration because she just finished the marathon. I have never seen her that happy as she was that day. Kayla biagiotti's body can't properly convert nutrients into energy. As a result, the 19-year-old's physical and mental development is stunted. Yeah, we're going to go for a run. Reporter: In may 2013, one month after the attacks, they ran a 5k race in Ashland, Massachusetts. There, they were finally awarded their Boston marathon medals. It was definitely very emotional. It helped us heal a little bit. Because you're trying to balance what happened on the negative side with, you know, being happy for what we have accomplished. And congratulations for that. Thanks to Tom Brady and ESPN. And we end with some good news -- the Pentagon report no deaths of service members in Afghanistan this week. Thanks for sharing part of your Sunday with us. Check out "World news" with David Muir tonight. I'll see you tomorrow on "Good morning America". In the meantime, take a look at the sign of spring, cherry

This transcript has been automatically generated and may not be 100% accurate.

{"id":23309720,"title":"'This Week': Boston Strong","duration":"2:52","description":"A preview of ESPN's special with Tom Brady on a unique mother-daughter team that survived the Boston Marathon bombing. ","section":"ThisWeek","mediaType":"Default"}